The international patent application No. PCT/SE2006/000212 filed Feb. 16 2006 with priority claimed from Feb. 16, 2005, discloses a system and method for regeneration of a fluid, in which synthetic urine is formed from a body fluid by only filtering and concentration. The synthetic urine will consequently include the substances and ions of the body fluid in the same proportions as in the body fluid but concentrated, except from larger molecules like albumin, which are filtered out before concentration. The body fluid may be plasma obtained from a plasma filter or peritoneal dialysis fluid obtained from the peritoneal cavity of a patient. Alternatively, the body fluid may be whole blood passed on one side of a semi-permeable membrane whereby the regenerated fluid is circulated on the other side of the membrane.
Because it is difficult to separate urea and creatinine from sodium and potassium, such substances are excreted in the synthetic urine in the same concentrations as found in the body fluid. While excretion of urea and creatinine is desired, excretion of sodium and potassium should be minimized. Small amounts of excretion can be replaced by oral intake.
The present invention starts from the fact that some patients produce creatinine at such a rate that the blood level of creatinine could reach poisonous levels if not excreted at high rates.